The brooch Michelle was wearing at the bar isn't on her dress anymore when she exits the car at the Stephens' home.
When Sam, disguised as the French temptress, departs, she tells Darrin "bonjour" (good day) but, in France, this greeting Is never used when departing, unless said in a vehement tone while being sarcastic, which Sam's Michelle wasn't. The problem lies in literal translating: if "bonjour" does mean "good day", in one word it is the equivalent of English's "good morning" and no one would say "good morning" when leaving. The correct salutation. therefore, should have been "au revoir".